(a) Field of the Invention:
The present invention relates to a pneumatic device such as lubricator adapted to atomize lubrication oil into an air stream circulating in an air-actuated device or to a filter for removal of dust or moisture from such air stream, and, more particularly, to a detachably attaching mechanism for a cup containing therein a quantity of lubrication oil or filter elements.
(b) Description of the Prior Art:
The lubricator, for example, usually comprises a cover provided with a substantially horizontal air conduit including an orifice, said air conduit extending through the cover, a cup for storage of oil and a protective cylinder mounted around said cup to avoid a danger that fragments of the cup might spatter when the cup possibly bursts under an excessive pressure built up therein, said cup and said protective cylinder being attached to the lower side of said cover, so that a difference between a pressure prevailing within the cup and a pressure prevailing within the orifice causes a quantity of oil contained within the cup to be sucked up and then to be atomized through the orifice into the air stream flowing therethrough. In such lubricator, there has conventionally been used the detachably attaching mechanism for the cup comprising: a plurality of locking projections equiangularly formed on the inner periphery of a circular connector ring defining the lower end of the cover along an open edge, a plurality of collar sections equiangularly disposed along and projecting from the outer peripheries of the respective open edges of both the cup and the protective cylinder, notches and projections formed in the cup and on the protective cylinder, respectively, to angularly position the cup and the protective cylinder so as to align the respective collar sections of the former with the associated collar sections of the latter, wherein the collar sections of the cup and the protective cylinder are fitted into the connector ring through the corresponding spaces defined between the respective pairs of adjacent locking projections of the cover and thereafter the cup and the protective cylinder are rotated together by a predetermined angle to lock the respective collar sections on the corresponding locking projections of the cover, a locking piece provided on the outer periphery of the protective cylinder, and means provided in the cover to receive said locking piece, preventing the cup and the protective cylinder from being rotated relative to the cover.
The aforementioned means to prevent the cup and the protective cylinder from being rotated relative to the cover has considered already been disclosed, for example, by Japanese Utility Model Unexamined Publication No. 59-81850, in which said means comprises a cut away window formed in the open edge of the protective cylinder, a locking piece extending from the bottom edge of said cut away window and having its front or top end depressible towards the centre of the protective cylinder against its own elasticity like a lever having said bottom side of the cut away window as a fulcrum, and a receiving groove correspondingly formed in the inner periphery of the connector ring of the cover along the open edge thereof, wherein the cup and the protective cylinder are fitted into the connector ring as the front or top end of the locking piece is slipped along the inner periphery of the connector ring, then the cup and the protective cylinder are rotated by a predetermined angle until the locking piece is received in the receiving groove under a restoring elasticity of the locking piece itself and thereby further rotation of the cup and the protective cylinder is prevented, and, to detach the cup, the locking piece is disengaged from the receiving groove by rotating the cup and the protective cylinder relative to the cover while said locking piece is held depressed. With such mechanism of well known art, the front or top end of the locking piece must be slipped along the inner periphery of the connector ring to achieve attachment and tilted towards the centre of the protective cylinder to disengage the locking piece from the receiving groove, so that there must be provided a relatively large gap between the inner periphery of the connector ring and the outer periphery of the protective cylinder. Such requirement disadvantageously results in a large diameter of the connector ring and therefore a bulky configurations.